Underwater vehicles (UVs), such as submarines, can be used for various applications, including military, scientific, and sightseeing applications. A military submarine can be very expensive to build. For example, it can cost about $750M for an SSK-class submarine and over $2 B for an SSN-class submarine, and it can take about 2 years to build. Such military submarines generally have about 60 to 100 crew members to operate in three shifts. There can be limitations for the command, control and communication in the deep ocean. There can also be a limited supply of oxygen for the engine and the crew to use. Other safety and security concerns are possible while operating a traditional military UV.
The basic maneuvering function of a UV in the ocean is based on buoyancy control. Buoyancy control can be achieved by a high pressure pneumatic valve control, which coordinates with the hull valve to regulate water intake and expression. These valves, together with the pipe connectors of the manifold system, can require regular human monitoring and manual maintenance because of the high pressure environment in the deep sea. The valves and pipe connectors can also be susceptible to unexpected failures during combat.
While underwater, a UV has a limited air supply for the engine and the crew members. Therefore, the UV has to surface to get air for the engine, to charge up the battery (e.g., for SSK-class submarines), and to pressurize air into storage for the crew. Similar to the buoyancy control equipment, the air storage apparatus needs pneumatic valve control monitoring and maintenance. While on the surface on the ocean, the UV can be in a vulnerable position during the combat mode.
A UV utilizes a periscope to observe other ships on the sea surface as well as to communicate with the command center. A typical UV periscope of an UV is approximately 50 feet in length. A mechanical/optical periscope can require precision parts and skilled assembly, contributing a major cost factor to building a UV. The wireless communication equipment can require a long antenna, and loss of power can occur due to the long transmission line used. While the periscope or the antenna is up within the periscope length, the UV can be in a vulnerable situation during combat mode.
The UV uses active sound navigation and ranging (sonar) for navigation. The UV can also use active sonar to detect surface vessels or surrounding adversary UV units. While using active sonar, a UV also exposes its position to adversary passive sonar monitoring, and this can lead to vulnerability for the UV. The active sonar emits strong ultrasonic or audible pulse waves at omni-direction and utilizes a hydrophone to detect the reflecting pulse wave to determine the position of the target and the target range.
The hull design and construction of a UV can be complicated and expensive, requiring the fabrication of many custom parts. A UV requires a high-pressure hull design which can lead to a heavier frame and reduced payload weight. A large shipyard is needed to construct a typical UV. This can require a longer lead time for construction versus the construction of, for example, a recreational vessel.